What’s the farthest object you’ll be able to see with solely your eyes? Until you reside beneath extraordinarily darkish skies unspoiled by mild air pollution, the reply is the Andromeda Galaxy (M31), positioned some 2.5 million light-years away. Touring throughout such an enormous, empty gulf reduces the mixed mild of M31’s estimated 1 trillion stars to a 4th-magnitude smudge that we are able to spot simply 1.5° west of Nu (ν) Andromedae.
The early twentieth century was a watershed second for the Andromeda Galaxy. In 1923, Edwin Hubble calculated the gap to M31 at 1 million light-years. Though later measurements confirmed this quantity was off, Hubble’s estimate put M31 past the recognized bounds of our galaxy, serving as the primary trace that the Milky Way was not the whole universe.
Categorised as a barred spiral galaxy just like the Milky Way, yard telescopes show Andromeda as a big, oval smudge of grayish mild. Spanning 3°, or six Full Moons positioned aspect by aspect, Andromeda will engulf your discipline of view. Take your time finding out it and you’ll discover a brilliant starlike core marking the middle of its disk.
A 4-inch or bigger scope exhibits that the galaxy’s southwestern edge gently fades away, whereas the northeastern edge abruptly halts. This latter sharp boundary is because of a skinny lane of opaque dust alongside the galaxy’s circumference. A second, dimmer outer dust lane, in addition to a dim adjoining glow, lies past, marking a separate spiral arm greedy out in our route.
Becoming a member of Andromeda are two dwarf elliptical satellite galaxies, M32 and NGC 205. M32 lies lower than half a level south of the guts of M31, whereas NGC 205 is as a substitute simply over half a level to its northwest. One other distinctive characteristic within the discipline is NGC 206, a big stellar affiliation in M31 containing greater than 300 spectral sort O and B stars. You’ll discover its comfortable glow about half a level southwest of M31’s heart.
Right this moment, the Andromeda Galaxy could seem comparatively dim to the bare eye. However it is going to ultimately get a lot brighter. In about 5 billion years, it is going to collide with our Milky Way, finally merging right into a single big elliptical galaxy.
Be sure that to discover Astronomy’s full list of 101 cosmic objects you must see. New entries shall be added every week all through 2022.
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